import sys

readline = sys.stdin.readline
readall = sys.stdin.read
ns = lambda: readline().rstrip()
ni = lambda: int(readline().rstrip())
nm = lambda: map(int, readline().split())
nl = lambda: list(map(int, readline().split()))
prn = lambda x: print(*x, sep='\n')

def solve():
    print('Yes' if ni() >= 30 else 'No')
    return

solve() import sys sys readline = sys.stdin.readline readline sys.stdin.readline sys.stdin sys stdin readline readall = sys.stdin.read readall sys.stdin.read sys.stdin sys stdin read ns = lambda: readline().rstrip() ns lambda: readline().rstrip() readline().rstrip() ().rstrip () readline rstrip ni = lambda: int(readline().rstrip()) ni lambda: int(readline().rstrip()) int(readline().rstrip()) int readline().rstrip() ().rstrip () readline rstrip nm = lambda: map(int, readline().split()) nm lambda: map(int, readline().split()) map(int, readline().split()) map int readline().split() ().split () readline split nl = lambda: list(map(int, readline().split())) nl lambda: list(map(int, readline().split())) list(map(int, readline().split())) list map(int, readline().split()) map int readline().split() ().split () readline split prn = lambda x: print(*x, sep='\n') prn lambda x: print(*x, sep='\n') print(*x, sep='\n') print *x x sep='\n' sep '\n' x def solve():
    print('Yes' if ni() >= 30 else 'No')
    return solve print('Yes' if ni() >= 30 else 'No') print 'Yes' if ni() >= 30 else 'No' ni() >= 30 ni() ni 30 'Yes' 'No' return solve() solve nm = lambda: map(int, readline().split()) lambda: map(int, readline().split()) nm readline = sys.stdin.readline sys.stdin.readline readline ni = lambda: int(readline().rstrip()) lambda: int(readline().rstrip()) ni nl = lambda: list(map(int, readline().split())) lambda: list(map(int, readline().split())) nl readall = sys.stdin.read sys.stdin.read readall ns = lambda: readline().rstrip() lambda: readline().rstrip() ns def solve():
    print('Yes' if ni() >= 30 else 'No')
    return def solve():
    print('Yes' if ni() >= 30 else 'No')
    return solve prn = lambda x: print(*x, sep='\n') lambda x: print(*x, sep='\n') prn
import sys

readline = sys.stdin.readline
readall = sys.stdin.read
ns = lambda: readline().rstrip()
ni = lambda: int(readline().rstrip())
nm = lambda: map(int, readline().split())
nl = lambda: list(map(int, readline().split()))
prn = lambda x: print(*x, sep='\n')

def solve():
    print('Yes' if ni() >= 30 else 'No')
    return

solve()
